The construction and application of asphalt to roads, paths and open spaces is an extremely complicated process. During this process the working result, i.e. the quality of the road surface produced, is not only determined by the adjustment of the machines, but also for example by the properties of the laying mixture (for example asphalt) and by the ambient conditions. Taken together all these parameters determine which quality, for example the smoothness, the road surface actually has.
Previously the machine operator defined the adjustment parameters of the machines. In doing this he oriented his task to the prevailing or the changing boundary or laying conditions—and to his experience. The more skill and experience of the machine operator in handling the relevant machine, the higher the quality of the road surface produced. On the other hand this quality may, however, also be very low if the machine operator has little experience or if he is confronted by previously unknown boundary conditions.
Some suggestions have already been made of how the adjustment of the machines can be arranged to be less dependent on the operator's experience. For example, EP 1 544 354 A2 suggests storing previous empirical values for advantageous operating parameter settings and using them again later as the basic setting for the machine. Starting from this basic setting, the operator only has to carry out fine adjustment of the machine.
German patent DE 40 40 029 C1 suggests setting the frequency of the drive of a compaction unit for a road construction machine in dependence of a predetermined laying rate and predetermined parameters of the layer to be laid. Here a set-point curve fur the temporal progression of the laying rate is specified.
International publication WO 00/70150 A1 and German patent DE 10 2008 058 481 A1 suggest measuring the temperature of a road surface just produced using a suitable sensor and controlling a road finisher or a following compaction machine according to the measured temperature.
A multi-channel control system for a road construction machine is furthermore known from German patent DE 195 37 691 C5. The control, however, only relates to the measurement of the temperature of a smoothing bar and maintaining it constant also in case of failure of a heater element. Feedback with other adjustment or laying parameters does not take place.
Finally, US patent publication 2004/0260504 A1 describes a system for the determination of the properties of a laying mixture. These properties are however only used for quality control and not for the control of the road construction machine.